Mounting concerns over the effect of greenhouse gases on global climate have focused attention on methods and systems for generating power and limiting greenhouse gas emissions. Solar power generation is particularly appealing because substantially no greenhouse gases are produced at the power generation source.
A concentrated or concentrating solar power (CSP) system collects solar energy and concentrates that energy onto an absorber. The absorbed optical energy provides a source of thermal energy to operate a power conversion cycle, for example a heat engine. The heat engine then produces electricity that is eventually fed into the electrical grid.
Concentrated solar power generation using solar receivers or collectors is also known. Briefly, concentrated solar power systems use lenses, mirrors, or other elements to focus sunlight from a relatively large area onto a small area called a solar receiver. The concentrated sunlight can be used to heat a fluid that serves as a thermal energy storage and transfer medium within the solar receiver. The fluid heated within the solar receiver can be used to drive a turbine to generate power.
For effective use of solar energy, the excess thermal energy needs to be collected and stored for later use, at times such as nighttime or cloudy days. A solar power tower uses focused solar radiation to concentrate solar power in a medium that can absorb and store thermal energy and later use it to generate steam from water or drive a turbine to generated electricity. These designs also allow power to be generated at a later time even when the sun is not shining.
Currently molten salts, mixtures of sodium nitrate and potassium nitrate, are employed as the thermal energy storage and transfer medium. Although these are non-flammable and non-toxic chemicals, they corrode the containing units. Thus, a more efficient thermal energy storage medium is required for more efficient and safer use of solar energy.